


Do I know you?

by KittytriesLipstick



Category: Undertale (Video Game)
Genre: Alternate Universe - Swapfell (Undertale), Explicit Language, Explicit Sexual Content, F/F, F/M, Graphic Description, Inspired by Kimi no Na wa. | Your Name., M/M, Multi, Other Additional Tags to Be Added, Reader is not Frisk or Chara (Undertale), Reader-Insert, Sharing a Body, Swapfell Papyrus (Undertale), Swapfell Sans (Undertale), Younger Brother Papyrus (Undertale)
Language: English
Status: In-Progress
Published: 2020-07-31
Updated: 2020-08-27
Packaged: 2021-03-05 19:26:58
Rating: Explicit
Warnings: Graphic Depictions Of Violence, Major Character Death
Chapters: 4
Words: 3,138
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25620559
Author URL: https://archiveofourown.org/users/KittytriesLipstick/pseuds/KittytriesLipstick
Summary: This is inspired by the movie your name.____ wakes up to find herself undead. A living breathing skeleton. With claws a shrill voice and shark teeth.In the middle of freaking out a taller skeleton opens the door glowing eyes of burnt orange fire.Once he finds out your not his brother he demands you go back. Thing is you don't know how._____________________Sans on the other hand can't believe his eyes. When he wakes up he has squishy flesh especially around his coccyx and ribcage. And human female in stripes walks in and makes a face."Mmmooooommmm ___ is touching her boobs again!"Who is this _____ and why is he in her body?
Relationships: Papyrus (Undertale)/Reader, Papyrus/Sans (Undertale), Sans (Undertale)/Reader
Comments: 38
Kudos: 101





	1. Who. Are you?

Some say that there's a red string connecting us to who were meant to be with.

A connection that transends time.

Laughs in the face of logic.

A connection that bonds you to the perfect person.

A person you might never meet.

But you dear _____

You made a wish on a star.

And I've heard your soul crying for the one you don't know you lost.

Just open your eyes and don't be scared.

Things won't always be this way.

_____________________

Your eyesockets open and you rub them sleepily. Ugh you slept terrible and for some reason your bed is harder than you remember falling asleep. 

Standing up you suddenly stumble and fall on the floor.

"OW! WHAT THE HELL IS WRONG WITH MY VOICE?!?!" Wait..... What is wrong with your hands?! Why are they bone!?

You touch your body and face frantically only to shiver and moan in shock when you touch some surprisingly sensitive part.

Your bone.

All bone.

Your dead-no undead.

You start hyperventilating and then it slowly works itself into a scream. 

"Milord! Are you ok?! Why are you-upf!" A strange tale skeleton with fangs rushes in making you scream louder and throw a fallen pillow in it's face.

You frantically scootch as far away as the wall will let you away from the skeleton.

"I DONT WANT TO BE DEAD! WHY AM I DEAD! I JUST FELL ASLEEP! WHATS GOING ON!? WHO ARE YOU? WHY AM I HERE!?"

The tall skeleton is frozen for a minute as it stares at you with it's fiery lights for eyes. When it growls you just shrink into yourself and whimper.

"Get out..... Get out of him!!!! Whoever or whatever you are your not welcome!!" 

You scream as he picks you up and throws you against the wall. Your pretty sure if you had bowels you would have shit yourself.

"I don't know what your talking about! I don't know what's going on! Please! You have to believe me! I'm.... Im Scared!!"

Seeing as your to frantic and terrified to make any sense he drops you on the bed. And looks at you thinking.

The way you hold yourself..... The strange change in soul... The way you flinch when you grab your for arm directly as you hug yourself....

"Are you a human?"

The distinct pack of harsh edges in your eyelights suggest your female.

"Y-yeah... I um just woke up like this. I don't know what's going on." You whisper softly your eyes filled with tears.

"Well whatever happened until we get it fixed yer gonna have ta take over his role. I'll take care of most of it *sigh* luckily I know everything about milord and he's on mandatory vacation right now."

He promptly picks you up and dresses you in spite of your struggles. When he's done your face is flushed and he scoffs.

"Hush up human. It's nothing I haven't seen before. Your in milords body. I always dress him up. Now get up before you scuff his nice house clothes."

You nod meekly on the brink of tears and scurry like a mouse downstairs behind him. What a weak creature. 

He supposed it's for the better that the one so happening to be stuck is so easily controlled.

Heh and milords heat is coming up soon. He might just take advantage of that. Especially since your fearful responses and meekness is kinda turning him on. Doesn't matter if you don't want to. Your just a human after all.

____________________

Sans wakes up and jolts onto the floor in shock. Why can he see out of both eyes and why is his ceiling purple?! 

He looks around warily. At least it's got black to and grey accents. The room is feminine and elegant tho.

He wonders if he blacked out and screwed a rich monster girl. His heat is nearing after all.

He looks around and goes to rub his face only to choke back a scream. 

He

Has

Fleshy bits!!!!

He spots a mirror and scrables over to it.

Holy shit.

He's a female. And a human.

A pretty one at that. To soft for his....oh hello. 

What are these things?

He grabs the fat over his ribcage and blush. It feels really good. He squeezes them both and plays with them until he finds the nipple. Pinching it he groans.

He decides he's going to learn this new body and use it to his advantage. 

Suddenly his room door opens and a small human girl looks at him.

"Mmmooooommmm!!! _______ is playing with her boobs again!!"

______? He's never heard of them.

He must be on the surface.

No telling how long he'll be in this body. Might as well learn what he can for his queen.

But first he must explore this body and act natural.

He has needs to and the mutts not here to take care of it.

Time to investigate.


	2. Chapter 2

You spent the whole day being taught how to act like sans. Posture. Speech patterns. How to summon bones. Fight patterns. Intimidation. Interrogation methods. Cooking.

Cooking was the hardest for you. At first you outright refused to put glass rocks and glue into the burritos. At least until mutt slammed his hand is on the counter at your sides and growled a warning in your ears.

"I HOPE YOU CHOKE ON THIS ABOMINATION." You hiss slamming it down in front of him before stomping upstairs and slamming the door of sanses room as you scream into a pillow.

You hate mutt so much right now. He rubs you the wrong way with his smarmy smile and his predatory hovering. Ugh. You feel sorry for this sans if he has to deal with papyrus all day every day. Mutt indeed. 

Your a lady. A dukes daughter. Not some tyrant royal gaurd who doesn't know how to cook.

With a sigh you sit by the window and meditate lightly a musical hum in your throat that's eerie. 

It helps you regain your composure when your upset. Your mom taught you that when you were little. The family song bird you became.

What's a sinner

But a slave to flesh

Filth to the eyes of God 

But the flesh never stays

It never holds them

Flesh has no love

A sinners truth

Is a missing piece

A piece even saints crave.

You didn't mean to start singing. Or to start crying but dammit your a gentle soul and your scared and papyrus has been helping but he hasn't been supportive. In fact he's been condescending and mean. 

Almost like he enjoys upsetting you to tears.

You fell asleep like that, purple tear tracks on your face slumped on the side of the window seat.

You don't hear a sigh. Nor do you feel yourself being stripped redressed or being set into bed.

"Didn't have to sing so sadly pigeon."

________________

Sans had to let a maid dress him in a corset and gown. Then he gets dragged off to lessons where he pays rapt attention. Especially politics. It's useful.

Then he throws a hissy fit at sewing singing and cooking lessons. He's a guard! A man! Well on the inside.

A man presumed to be the father of this body's owner grabs his arm and demands to know what's gotten into him.

Realising he's acting out of character he stops and reluctantly apologizes. A maid suggests maybe he's on his period and that's the end of it.

He spends the rest of his time reading the girls diary.

Song lyrics. Boring.

Poetry. Kinda sad.

Ranting about her father's politics. Useful.

Oh. Hello.

Mt ebbot is right outside the city?   
It says she visits the monument once a week.

Extra useful.

She sounds like a bird in a gold cage.

Kinda cute.

He used to read books about maidens like this.

That he'd rescue a princess locked in a tower.

He wonders if she's in his body. Mutt would take care of her. It's his body after all. 

Maybe once they take over topside he'll take her as a pet. 

He skips dinner and explores the grounds and more of her diaries. 

He's falls asleep looking through her art journals.


	3. Chapter 3

You wake up with a start with your journals around you.

Your back.

You can't believe it. You have boobs again!

Not important to most but you.  
You sniffle trying not to cry as you squeeze them. Your back and safe and you have boobs and your not a skeleton and and.

"Mmmooooommmm _____ is being weird! Make her stoooooopppp!! I hope I don't play with my boobs when I grow up." Your sister makes a gagging face that makes you laugh.

Letting your personal maid dress you you listen to her tell you about how strange you were yesterday.

So it wasn't a dream? 

Wait…..

HE SAW YOU NAKED!!!!

Your face flushes darkly at the thought and you cover your face. You've been seen bare before marriage! You can't be wed now!

Well… no one knows cause it was technically you. It just has to stay that way. 

After your dressed you write in your diary and hole up in your room.

'just in case this happens again since you clearly read my diary. Most likely to learn more sans. Why don't we set up a system so we stay current with what's happening. 

First off your cooking sucks. Listen to the teachers advice. It'll help you.

Take notes for me to read so I don't get behind in lessons.

The woman calling herself my mother is a gold digging wench. Feel free to discreetly let her know as much as you want. The only good thing she brought is my half sister jenny.

Play with her sometimes. She gets lonely and no one will give her the time if day.

Never wear pink in my body. People will get suspicious because I hate it. I like purple.

It's soothing.

Also spend at least an hour in the garden. It's something I usually do.

I got taught a lot about you.

Perhaps take the occasional not mandatory break? You'll burn out if you don't.

Also if your having trouble with singing use a tuning whistle. It'll help you find the pitch.'

You end up writing a lot more after that. More than you planned to. After that tho you start drawing. You meant to draw roses but then it turned into a skeleton.

Sans. Walking in your garden. Staring out his window. Burning food. Throwing a tantrum. Smacking mutt. Fighting your father.

A shock goes through your body and you gasp panting and clutching your chest.

It looks so real. 

The detail so careful. 

It scares you a little.

______________

Sans wakes up groaning and his back creeking from the stiff mattress. Damn that dream world bed must've spoiled him.

Looking at the clock he sighs. Four in the morning. With a sigh he waits for the mutt to come and dress him.

When he does he seems to slump. "Your back." Was that disappointment? How rude. At least he knows it wasn't a dream at all now.

"OF COURSE ITS ME YOU DISGUSTING CREATURE. NOW DRESS ME. IVE GOTTEN AHOLD OF SOME IMPORTANT INFORMATION FROM THE SURFACE I NEED TO REPORT IMMEDIATELY."

"Sorry milord. Mandatory leave is still in place until after the yearly quarantine. So traveling for anything other than rations is forbidden. You'll just have to write it down until then." 

Sans growls frustrated. He's not dumb enough to believe it was a dream especially since the mutt confirmed it.

He has the mongrel fill him in and he writes a list of rules for the female. just in case. There's no way In hell he's going to have a human maiden ruin his image. Or abused by his useless greasy brother.

He hides it under his pillow before making a report to send immediately after quarantine. 

There's a strange disease that's been twisting the infecteds magic and turning them feral. It's lethal to weaker monsters but it permanently alters stronger monsters. It spreads it's pores once a year around spring.

And he's needed as the captain to retain proper cognizance. So he and the few boss monsters left after the first wave are quarantined until undyne and a few other rare immune types clean up the offending spores. However they don't know where the hive spores are. And the be been searching for years. 

Granted it was undynes bio warfare disease but some foolish monster thought they could steal it and sell it on the black market. 

Idiots.

Luckily undyne knows the cure and how to sanitize the areas.

She always did come prepared like that.

Rather convenient timing for him. He doesn't have to request leave for his heat. 

The next three days go by without change and he almost thinks the whole body swap thing is over.

But then he opens HER eyes.


	4. Chapter 4

It had been three days. Three days of no changes no body swaps. You had almost forgotten about that weird day and the sketches.

But today. Today your sans. You didn't even need to open your eyes. The feeling of that horrible mattress underneath you says it all. With a sigh you sit up only for a paper to crumple under your hand.

It's a note of rules and tips similar to the one you left him.

SINCE IT APPEARS WE'VE SWAPPED BODIES IVE DECIDED TO LAY OUT SOME RULES FOR YOUR TIME HERE.

THIS IS TO PROTECT YOU AND MYSELF AS WELL AS MY USELESS BROTHER.

KNOWING MY BROTHER HE WILL MOST LIKELY ATTEMPT TO CORNER YOU AND DO NASTY THINGS. TELL HIM TO SIT AND HE WILL HAVE NO CHOICE BUT TO OBEY.

BE SURE TO WRITE IT DOWN AND HIDE IT UNDER THE FLOOR BOARD. I WILL PUNISH HIM ACCORDINGLY. 

WE ARE IN THE MIDST OF A YEARLY QUARANTINE SO NO GOING OUTSIDE AND IF MY BROTHER GOES OUT WAIT TILL HES SHOWERED TO APPROACH.

ONCE QUARANTINE IS OVER I WILL ADD MORE.

How sweet. For a rude skeleton that fondled your body.

You got an earful from your stepmother about being a better influence and the importance of being conservative with your body. She says as she wears a corset top dress with her tits half hanging out. 

Woman probably slept with most of the staff in the main building. 

You get up and attempt to dress yourself before papyrus gets up only to fail miserably. Why do rich people have people dress them? It just makes it complicated. What if you suddenly become poor.

Struggling with your buttons you let out a squeal when two bony arms wrapped around you.

"So your back… I missed messing with ya pidge." His oddly sort of clove scented breath is hot against your neck.

"Quarantine ends in two weeks. But sans goes into heat in three days. Ever have sex before? Because that's all your going to crave if you happen to be here during."

"I-ITS TO EARLY TO BE MAKING SUCH COMMENTS. AND HIGHLY INAPPROPRIATE TO EVEN MENTION IT TO A LADY! NO MAN WOULD HAVE ME IF I WERE SOILED BEFORE MARRIAGE!" You Huff angrily and shove him off you only for him to shove you against the wall with a predatory growl.

"A virgin eh? Listen pidge. The only way a person could deflower you is if your actual body has sex. My job is to take care of milords and now your needs regardless of whether you want it or not. I just thought I'd let you know. But since you have never done such a thing I'll go easy on you."

You tear up your face flushed and he sighs petting your head. "Don't look at me like that pidge. I think you'll find you'll like it"

"SEX IS A WOMANS DUTY TO HER HUSBAND. ITS NOT AN ENJOYABLE THING. EVEN MY STEP MOTHER JUST USES IT FOR LEVERAGE." You shake hard choking on sobs. Your going to be raped because your in a man's body.

"Woah woah woah. Who the hell decided a woman can't enjoy sex?" You shake your head covering your eyes and sobbing. He's gotten himself in quite the pickle.

How does he fix this? Perhaps with the thing she's scared of. Clearly she has a skewed vision of what sex is. Maybe…

"Shhhhhh…. Let me show ya something ok? I'm not gonna take ya just gonna show you it's ok to feel good. Can't have you stressing after all. Hey hey none of that now. ssshhhhhhshshshshshh…"

He cups your face. It's hard to see his brother when your making such cute faces. It's almost like his Bros body isnt here and it's a girl look a like. Like their twins.

You try to move your face away in fear only for his teeth to clink against yours. You scrunch your face waiting for the gross wet kissing and tongue down your throat you were expecting only to receive...tingling warmth. 

He nuzzles his teeth against yours. It's been forever since he's done anything remotely vanilla like this. He wonders how far he can get you.

You shake but your not pushing him away so he presses his body closer and guides his tongue slowly into your mouth. To which you struggle a little only to relax when he doesn't just shove it deep in your throat and choke you with it.

It's careful…. Warm…. It…. It feels good. Is this what sin is like?

Eventually you push him away but only because you need to breath. Or at least… you think you do.

Is it wrong of him to take advantage of you? Probably. But it honestly doesn't matter. Your just a human.

Well a cute one. That can sing. And makes his brothers mouth taste sweet. He wonders if his brothers ecto changed to.

Might as well find out. Later tho. You look like you've had enough. He'll just take care of his arousal later. First he needs to set you up with that monster history book to study. 

________

Sans wakes up in luxury. Silks on his skin and cushy pillows. 

A diary sits next to a glass of sweet water in a bedside table. Picking it up he looks inside. It's a recap of the last three days and a note to him. 

"How dare she!!!!! My cooking is amazing! Though I suppose humans have more primitive tastes…." Very well. He decides. He will learn and master the human culinary arts.

As for the rest he was already going to do. Well except for the entertaining the child thing. However since he expects rules he made for his body to be followed he will oblige your requests.

First order of business. Insulting that wench.


End file.
